In recent years, various research into disposing objects having various functions on an inner circumferential surface of a pneumatic tire has been conducted.
For example, an attaching method has been proposed in which tire tags (for example, radio frequency identification tags), chips, or the like are attached to the innerliner or the like of a raw tire using a surface fastener such as a hook and loop fastener, a hook and hook fastener, or the like (see Japanese Unexamined Patent Application Publication No. 2005-517581A).
Additionally, a pneumatic tire has been proposed in which a surface fastener is vulcanization bonded to a region of the tire inner surface corresponding to a tread portion, and a noise absorbing member is attached to the tire inner surface via the surface fastener (Japanese Unexamined Patent Application Publication No. 2006-44503A).
The surface fasteners proposed in Japanese Unexamined Patent Application Publication Nos. 2005-517581 and 2006-44503A have been preferable configurations in that relatively strong engagement force is realized when attaching, and engagement on a surface can be achieved without slight misalignments when attaching becoming a problem.
However, with surface fasteners, a state in which the individual engaging elements of the surface fastener are engaged with one another is not ideal due to the inner circumferential surface of the pneumatic tire being an annular, curved surface. With surface fasteners, portions of the edges and center portions become raised, and an amount of obtained engagement force varies (positional variation within the tire and variation from tire to tire). As a result, in some cases, the expected engagement force has not been obtained. Additionally, deterioration and/or declining over time of the engagement force of an entirety of the surface fastener accompanying the occurrence and progression of the partial physical deterioration occurs as a result of repetitive deformation and compaction over an extended period of time caused by rotation at high speeds in a state of relatively elevated temperatures. This has led to cases in which difficulties have been met in maintaining a desired engagement force over an extended period of time.
Furthermore, although surface fasteners have been preferable in that engagement on a surface can be achieved without slight misalignments when attaching becoming a problem, when the attached functional object is, for example, a measuring device, a way to more reliably and precisely attach the object to a position has been demanded. Because of this lack of reliable and precise attachment, there have been functional objects not suited to being attached with a surface fastener.
Also, the present inventors have previously proposed a pneumatic tire whereby a desired engagement force can be maintained over an extended period of time, the engagement force physically deteriorating or declining over time due to extreme usage conditions, including repetitive deformation and compaction over an extended period of time caused by tire rotation at high speeds in a state of relatively elevated temperatures, to a minimal degree. The obtained engagement force is great and is essentially free of variations in strength (positional variation within the tire and variation from tire to tire). Specifically, a pneumatic tire is proposed in which types of objects with desired functions are attached by bonding mechanical fasteners, known as hooks or snaps, to a tire inner surface (see Japanese Unexamined Patent Application Publication Nos. 2012-25318A, 2012-25319A or 2012-240465A).
As described in the scope of the claims of exemplary Japanese Unexamined Patent Application Publication No. 2012-25318A, specifically, a pneumatic tire is proposed provided with a first fastener of a separable pair of mechanical fasteners, such as hooks or snaps, on the tire inner surface (claim 1 of the scope of the claims of Japanese Unexamined Patent Application Publication No. 2012-25318A). More specifically, a pneumatic tire is proposed wherein the first fastener comprises at least two components, the two components being fixed together to form the first fastener by sandwiching a tire member or a tire reinforcing member (claim 2 of the scope of the claims of Japanese Unexamined Patent Application Publication No. 2012-25318A).
According to the methods described in Japanese Unexamined Patent Application Publication Nos. 2012-25318A, 2012-25319A and 2012-240465A of attaching a desired object by bonding a mechanical fastener (hooks or snaps) to a tire inner surface, an object can be engaged and attached to a tire inner surface via such a mechanical fastener. Also, according to the methods, the obtained engagement force is typically great and is essentially free of variations in strength (positional variation within the tire and variation from tire to tire). Furthermore, the object can be attached at a predetermined position in a precise manner. As a result, a superior pneumatic tire is achieved whereby a desired engagement force can be maintained over an extended period of time, the engagement force deteriorating or declining over time due to repetitive extreme usage conditions over an extended period of time to a minimal degree.
In particular, by using, as the first mechanical fastener attached to the tire inner surface, a fastener that comprises at least two components, the two components fixing together to form the first fastener by sandwiching a tire member or a tire reinforcing member, a more superior mechanical fastener with increased fixing strength and good durability is achieved.
However, with the configurations of the methods described above, when a large object is attached, the mechanical fastener may be required to be attached in a state protruding from the tire inner surface by a certain degree. Also, when a heavy object is attached, the bonding strength between the tire inner surface and the mechanical fastener may be insufficient.
Notably, when a comparatively large, heavy specific functional object is attached to a tire inner surface, in particular a curved tire inner circumferential surface, the mechanical fastener requires a large protruding height so that the object and the inner circumferential surface do not interfere with each other. Also, in the majority of cases in which only one mechanical fastener (one pair) is used to fasten, as the force applied upon fastening cannot be distributed, enhancing the fixing strength to the tire inner surface is desirable. In other words, in most cases, mechanical fasteners cannot be added to the configurations after the tire is formed, and because the configurations in essence use one fastener to fasten, a pair of fasteners is needed which can be applied to the attachment of each type of the functional objects, and if a plurality of fasteners are used for fastening, pairs that correspond in number and position on both sides including the side of each type of functional object to be attached. As a result, versatility is unfortunately decreased.
Moreover, Japanese Unexamined Patent Application Publication No. 2012-25318A describes a mechanical fastener preferably having a height of a portion that protrudes most from the tire inner surface from 0 mm to 3 mm (Japanese Unexamined Patent Application Publication No. 2012-25318A, paragraph [0029]). A fastener having a protruding height greater than that range is not recommended.
This may be because when a mechanical fastener has a large protruding height, the bonding strength and durability of the mechanical fastener itself may become insufficient, regardless of the dimensions, weight, and other characteristics of each type of the attached functional objects. In particular, the present inventors believe that a contributing factor to this is that when a mechanical fastener member with a large protruding height is provided, the actions and functions of the bladder are interrupted around the mechanical fastener member.
Two assumed factors arising when the protruding height is large are detailed below.
(a) Upon vulcanization, although the pressure applied to the vulcanization bladder transmits to the tire, the pressure is insufficiently applied to the tire at the portion where the fastener with a large protruding height is located due to a space (see space X of FIG. 3) forming between the fastener and the vulcanization bladder. As a result, the rubber is insufficiently vulcanized. Consequently, the strength of the rubber or rubberized filler where the fastener is embedded inside the tire decreases, causing the durability of the fastener to decrease.
(b) Upon initiation of the vulcanization of a tire, the vulcanization bladder develops (expands) inside the tire. However, when the surface of the bladder and the tire surface move and rub against each other in the surface direction, the fastener with a large protruding height is subject to lateral force in a specific direction and is not fixed in a straight manner. As a result, the durability of the fastener decreases.